Light-transmitting metal oxides are used in semiconductor devices. For example, conductive metal oxides (hereinafter referred to as oxide conductors) such as indium tin oxide (ITO) are used as transparent electrode materials needed in display devices such as liquid crystal displays.
In addition, light-transmitting metal oxides attract attention as materials having semiconductor properties. For example, In—Ga—Zn—O-based oxides and the like are expected to be used as semiconductor materials needed in display devices such as liquid crystal displays. In particular, they are expected to be used for channel layers of thin film transistors (hereinafter also referred to as TFTs).
TFTs which include metal oxides having semiconductor properties (hereinafter referred to as oxide semiconductors) can be formed by low-temperature processes. Thus, expectations for oxide semiconductors as materials which replace or surpass amorphous silicon used in display devices and the like are increased.
Further, oxide conductors and oxide semiconductors have light-transmitting properties. Thus, by forming TFTs with the use of these materials, light-transmitting TFTs can be formed (for example, see Non-Patent Document 1).
Furthermore, TFTs including oxide semiconductors have high field effect mobility. Thus, driver circuits in display devices or the like can be formed using the TFTs (for example, see Non-Patent Document 2).